Pumps are generally known and used for a variety of applications in transmissions and transfer cases. One of the most common ways pumps are used in these types of applications is for the generation of fluid pressure which can be used to actuate clutch assemblies or the like. One particular type of pump commonly used in transmissions and transfer cases is what is known as a “gerotor pump.”
A gerotor pump usually consists of an inner gerotor which is mounted on a shaft, and an outer gerotor which circumscribes the inner gerotor. The inner gerotor usually has a series of lobes which are engagable with a corresponding series of lobes on the outer gerotor such that the inner gerotor transfers rotational force to the outer gerotor as the shaft and inner gerotor rotate. However, the outer gerotor usually has a larger number of lobes such that the diameter of the inner gerotor and the outer gerotor are different. The space between the inner gerotor and outer gerotor created by the different number of lobes causes a pumping action to be created when the inner gerotor and outer gerotor rotate.
A common drawback well known with gerotor pumps is an inability to deactivate the gerotor pump. The inner gerotor is typically mounted on the shaft through the use of a spline connection, and because the shaft is rotating, the inner gerotor is constantly driving the outer gerotor as the shaft rotates, regardless of whether a pumping action is needed or not. This often leads to situations where pumping action by the gerotor pump is unnecessary. Having these types of pumps active when the pumping action is not necessary can reduce the efficiency of the transmission or the transfer case.
Accordingly, there exists a need for a pump powered by a rotating shaft in a transmission or a transfer case which is selectively engagable.